Comparison of digital lock-in amplifier and fast fourier transform algorithms for quartz-tuning-fork enhanced spectrosco
- PDF / 1,091,531 Bytes
- 12 Pages / 439.37 x 666.142 pts Page_size
- 58 Downloads / 192 Views
Comparison of digital lock‑in amplifier and fast fourier transform algorithms for quartz‑tuning‑fork enhanced spectroscopy Daojun Liu1 · Ningwu Liu2 · Sheng Zhou2 · Jingsong Li2 Received: 6 June 2020 / Accepted: 29 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A near-infrared methane (CH4) gas sensor system was implemented using a quartz crystal tuning fork (QCTF) based photoelectric detector and a fiber-coupled distributed feedback diode laser emitting at 1.653 μm. Wavelength-modulation with second-harmonic (2f) detection method was investigated. For signal processing, two different demodulation algorithms, i.e. Fast Fourier Transformation (FFT) and digital lock-in amplifier (DLIA), were developed and completely compared for harmonic signal extraction. Experimental results show that the SNR of WMS-2f signals using the proposed FFT algorithm can be improved by 2.5 times on average than the common DLIA method, which agrees well with the theoretical value of 2.7 times achieved with the simulated spectra data. In comparison, the proposed FFT algorithm shows better performance on signal processing efficiency and simplification, when a QCTF was used as a photoelectric detector or an acoustic transducer. Keywords Quartz enhance spectroscopy · FFT · DLIA · WMS-2f
1 Introduction Atmospheric methane (CH4) is a significant greenhouse gas by influencing tropospheric ozone (O3) and stratospheric water vapor (H2O), with a warming impact of 25 times greater than carbon dioxide (CO2), and the emission of CH4 will cause further warming and a continuous change of global climate system (Pachauri et al. 2014). The globally atmospheric CH4 concentration reached ~ 1.8 parts per million by volume (ppmv) in 2016 with ~ 2.6 times of the pre-industrial level (~ 722 ppbv) (World Metrological Organization 2016). Moreover, CH4 is also known as an industrial safety hazard, especially in natural gas and coal mining industry, and a biomarker linked to gut bacteria in clinical medicine (Zhang et al. 2014). Thus, numerous technologies have been employed for C H4 detection, including
* Jingsong Li [email protected] 1
Department of General Education, Anhui Xinhua University, Hefei 230088, China
2
Key Laboratory of Opto‑Electronic Information Acquisition and Manipulation of Ministry of Education, Anhui University, Hefei 230601, China
13
Vol.:(0123456789)
417
Page 2 of 12
D. Liu et al.
chemical method and optical techniques. In comparison, tunable diode laser absorption spectroscopy (TDLAS) as an infrared absorption spectroscopy technique is widely used in the field of trace gas measurement, due to numerous advantages including fast response, non-intrusive and sensitive species-specific detection capabilities (Wolff et al. 2013; Wang et al. 2015; Wei et al. 2015). Wavelength modulation spectroscopy (WMS) with a significant ability to suppress noise and achieve high signal-to-noise ratio (SNR) as well as high measurement sensitivity is broadly adopted in C H4 detection (Sur et
Data Loading...
